I think there is a small amount of risk to go on AS as a G7, but it's not an unreasonable choice. Here is a discussion on it that might be useful to you
/prostatecancerinfolink.net/2017/07/22/low-volume-gleason-3-4-7-disease-is-active-surveillance-a-realistic-option/I think the main takeaway is that if your first biopsy wasn't MRI targeted (or MRI showed nothing), you should get a multiparametric MRI before your next biopsy and if positive, get a MRI targeted fusion biopsy. Your ability to stay on AS is, to some extent, due to the your low cancer volume i.e., only one core sample was positive. However, as you might know, biopsies are not very precise as they spread out the 12 needles. It's quite possible that some cancer was missed. If something shows up on the MRI, they will target that area more intensively on the biopsy, which may help you decide to stay on AS or not.
Bone scans at this stage are not very useful